NAME

       PSLASET - initialize an M-by-N distributed matrix sub( A ) denoting A(IA:IA+M-1,JA:JA+N-1)
       to BETA on the diagonal and ALPHA on the offdiagonals

SYNOPSIS

       SUBROUTINE PSLASET( UPLO, M, N, ALPHA, BETA, A, IA, JA, DESCA )

           CHARACTER       UPLO

           INTEGER         IA, JA, M, N

           REAL            ALPHA, BETA

           INTEGER         DESCA( * )

           REAL            A( * )

PURPOSE

       PSLASET initializes an M-by-N distributed matrix sub( A ) denoting  A(IA:IA+M-1,JA:JA+N-1)
       to BETA on the diagonal and ALPHA on the offdiagonals.

       Notes
       =====

       Each  global  data  object  is described by an associated description vector.  This vector
       stores the information required to establish the mapping between an object element and its
       corresponding process and memory location.

       Let  A be a generic term for any 2D block cyclicly distributed array.  Such a global array
       has an associated description vector DESCA.  In the following comments,  the  character  _
       should be read as "of the global array".

       NOTATION        STORED IN      EXPLANATION
       ---------------   --------------   --------------------------------------  DTYPE_A(global)
       DESCA( DTYPE_ )The descriptor type.  In this case,
                                      DTYPE_A = 1.
       CTXT_A (global) DESCA( CTXT_ ) The BLACS context handle, indicating
                                      the BLACS process grid A is distribu-
                                      ted over. The context itself is glo-
                                      bal, but the handle (the integer
                                      value) may vary.
       M_A    (global) DESCA( M_ )    The number of rows in the global
                                      array A.
       N_A    (global) DESCA( N_ )    The number of columns in the global
                                      array A.
       MB_A   (global) DESCA( MB_ )   The blocking factor used to distribute
                                      the rows of the array.
       NB_A   (global) DESCA( NB_ )   The blocking factor used to distribute
                                      the columns of the array.
       RSRC_A (global) DESCA( RSRC_ ) The process row over which the first
                                      row of the array A is distributed.  CSRC_A (global)  DESCA(
       CSRC_ ) The process column over which the
                                      first column of the array A is
                                      distributed.
       LLD_A  (local)  DESCA( LLD_ )  The leading dimension of the local
                                      array.  LLD_A >= MAX(1,LOCr(M_A)).

       Let  K  be  the  number  of  rows  or columns of a distributed matrix, and assume that its
       process grid has dimension p x q.
       LOCr( K ) denotes the number of elements of K that a  process  would  receive  if  K  were
       distributed over the p processes of its process column.
       Similarly, LOCc( K ) denotes the number of elements of K that a process would receive if K
       were distributed over the q processes of its process row.
       The values of LOCr() and LOCc() may be  determined  via  a  call  to  the  ScaLAPACK  tool
       function, NUMROC:
               LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
               LOCc(  N  )  =  NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ).  An upper bound for these
       quantities may be computed by:
               LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
               LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A

ARGUMENTS

       UPLO    (global input) CHARACTER
               Specifies the part of the distributed matrix sub( A ) to be set:
               = 'U':      Upper triangular part is set; the strictly lower  triangular  part  of
               sub(  A  )  is not changed; = 'L':      Lower triangular part is set; the strictly
               upper triangular part of sub( A ) is not changed; Otherwise:  All  of  the  matrix
               sub( A ) is set.

       M       (global input) INTEGER
               The  number  of  rows  to be operated on i.e the number of rows of the distributed
               submatrix sub( A ). M >= 0.

       N       (global input) INTEGER
               The number of columns to  be  operated  on  i.e  the  number  of  columns  of  the
               distributed submatrix sub( A ). N >= 0.

       ALPHA   (global input) REAL
               The constant to which the offdiagonal elements are to be set.

       BETA    (global input) REAL
               The constant to which the diagonal elements are to be set.

       A       (local output) REAL pointer into the local memory
               to  an  array  of  dimension  (LLD_A,LOCc(JA+N-1)).  This array contains the local
               pieces of the distributed matrix sub( A ) to be set.  On exit, the leading  M-by-N
               submatrix sub( A ) is set as follows:

               if  UPLO  =  'U',  A(IA+i-1,JA+j-1)  =  ALPHA,  1<=i<=j-1, 1<=j<=N, if UPLO = 'L',
               A(IA+i-1,JA+j-1) = ALPHA, j+1<=i<=M, 1<=j<=N,  otherwise,      A(IA+i-1,JA+j-1)  =
               ALPHA, 1<=i<=M, 1<=j<=N, IA+i.NE.JA+j, and, for all UPLO, A(IA+i-1,JA+i-1) = BETA,
               1<=i<=min(M,N).

       IA      (global input) INTEGER
               The row index in the global array A indicating the first row of sub( A ).

       JA      (global input) INTEGER
               The column index in the global array A indicating the first column of sub( A ).

       DESCA   (global and local input) INTEGER array of dimension DLEN_.
               The array descriptor for the distributed matrix A.